iOS 请求状态区域在 didStartMonitoringFor 之后返回 .unknown

Question

对为什么我的AppDelegate CLLocationManager有时无法成功确定CLRegionState（CLRegionState.unknown）感到困惑，即使我确保在didStartMonitoringForRegion之后才调用requestStateForRegion。似乎是某种我不明白我如何处理的竞争条件。

相关，当我得到CLRegionState.unknown时，我应该怎么做？继续请求状态，直到我得到一些东西？（这似乎很糟糕）

应用代表：

- (BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions
{   
    self.locationManager = [[CLLocationManager alloc] init];
    [self.locationManager setDelegate:self];
    return [super application:application didFinishLaunchingWithOptions:launchOptions];
}
- (void)locationManager:(CLLocationManager *)manager didStartMonitoringForRegion:(nonnull CLRegion *)region {
    NSLog(@"%@", [NSString stringWithFormat:@"didStartMonitoringFor region with ID: %@", region.identifier]);
    // delay per https://stackoverflow.com/a/33288103/3380970
    double delayInSeconds = 2.0;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void) {
        [self.locationManager requestStateForRegion:region];
    });
}
- (void)locationManager:(CLLocationManager *)manager didDetermineState:(CLRegionState)state forRegion:(nonnull CLRegion *)region {
    NSLog(@"%@", [NSString stringWithFormat:@"didDetermineState from AppDelegate CLLocationManager: %@ (%ld)", region.identifier, (long)state ]);
    NSString *baseUrl = [self fetchBaseUrl];
    switch (state) {
        case CLRegionStateInside:
            NSLog(@"%@", @"Determined .inside state for geofence");
            [HelperFunctions postGeofenceTransitionWithBaseUrl:baseUrl region:region transitionType:1];
            break;
        default:
            break;
    }
}

原始日志：

Adding geofence with ID: 5:90fd74e0-cbc7-dbe5-20fc-b870203055e1    
Adding geofence with ID: 8:d408f466-ea1b-6cbb-382f-f7567db61157
Adding geofence with ID: 7:ba97dda2-39a7-9b95-8ea9-ea183d69a858
didStartMonitoringFor region with ID: 5:90fd74e0-cbc7-dbe5-20fc-b870203055e1
didStartMonitoringFor region with ID: 8:d408f466-ea1b-6cbb-382f-f7567db61157
didStartMonitoringFor region with ID: 7:ba97dda2-39a7-9b95-8ea9-ea183d69a858
didDetermineState from AppDelegate CLLocationManager: 5:90fd74e0-cbc7-dbe5-20fc-b870203055e1 (0)
didDetermineState from AppDelegate CLLocationManager: 8:d408f466-ea1b-6cbb-382f-f7567db61157 (0)
didDetermineState from AppDelegate CLLocationManager: 7:ba97dda2-39a7-9b95-8ea9-ea183d69a858 (0)

谢谢

Answer 1

这是因为您在块内使用条目参数region，而没有使其成为块变量。

在- (void)locationManager:(CLLocationManager *)manager didStartMonitoringForRegion:(nonnull CLRegion *)region {中添加：

__block CLRegion *blockRegion = region;

并在您的块中使用blockRegion。

Answer 2

每当你想要使用 requestStateForRegion 时都要小心。此方法可能会生成有关设备的当前位置的错误结果。由于我在LTE上使用不同的网络进行了一些实验，因此它会错过某些地区的某些状态，并且在WIFI上，我看到它会产生重复的计数器事件，例如对于位置A，它产生了进入和退出两个。我你仔细阅读了苹果文档下此方法的评论，它说

异步检索指定区域的缓存状态。

此缓存状态不准确。